Suspect someone’s been using your Mac when you’re not around, even though you told them not to? Find out, without the need for special software.

You could physically dust your Mac for fingerprints, of course, but if you lack the gear for that don’t worry: there are digital tools you can use for this detective work. You’ll be amazed at what you can find out just by checking logs and looking at recently open documents and applications.

Step 1: Check The Logs

Your Mac logs a lot of things. Obsessively. Open up the Console if you don’t believe me – this app gives you a simple way to explore a wide variety of logs. You’ll find it in Utilities, which is in your Mac’s Applications folder. Open it up for the first time and you’ll mostly see gibberish:

It’s almost a record of everything that ever happened on your computer, and it can be completely overwhelming.

So, how does this help you? If you can narrow it down to just relevant points of information, a lot. Perhaps the most helpful thing is to see a list of every time your computer woke up, and doing just that is simple. Type “wake reason:” into the search bar and you’ll see when that happened:

Click the “earlier” button at the bottom to go further and further back into time. You know something might be fishy if your computer woke up some time while you were out of the house.

There’s a quicker way to do this, if you’re comfortable with the Terminal: just type syslog |grep -i "Wake reason" and you’ll see a longer list:

Knowing when your computer wakes up might not be enough – cats pressing keyboard keys can be enough to prompt this. But if you’re using a MacBook you’ll know exactly when someone opened it to use your computer, and that’s helpful.

This won’t tell you who is using your computer, of course, or what they did. But it’s a good place to start.

Step 2: Check Recent Items

Your Mac keeps track of recently opened applications and documents. It does this mainly to help you quickly access them again, but it’s also really useful if you suspect someone else is using your computer. After all, they’ll probably be interested in different applications and documents than you are.

See a list of all recent applications and documents by clicking the Apple logo at top-right, then hovering over “Recent Items”. You’ll see a list:

Hold Command and you can click to see these files in Finder, giving you access to information like when they were last opened.

Speaking of: newer version of OS X offer similar functionality to this in the Finder itself. You’ll see recently opened documents, pictures, movies and more broken down into categories on the All My Files shortcut:

If you find something here you know you didn’t look at recently, congratulations: you’ve got one more piece of evidence that someone else is using your Mac while you’re not around.

There are other “Recent” things to check, of course, beyond what your Mac records on its own. Your web browser, for example, includes a detailed web history. Applications like Microsoft Word and InDesign have their own list of recently opened documents. Check these and other things if you want to gather further evidence.

Bonus Step 2: Kill It With Passwords

But there’s an even simpler solution: lock your Mac with a password. If you don’t want people using your computer behind your back this is the most effective means of doing so.

If you’d rather not do that, however, you should get a pretty good idea of who’s using your Mac with the first two steps – between the logs and the recent apps a decent detective should be able to rule out most major suspects. The rest, of course, is up to you – unless you use Prey to capture a picture of the culprit.

I want to know which tools you think are most useful for this job, and which have worked for you. Share your battle stories in the comments below.

How could I find out if someone has backed up my macbook air to an external hard drive/stick? I have not backed it up in this manner since purchase but am beginning to wonder if someone else has...? Answer for idiots please, as you can tell I am not very tech savvie Thanks

I have had my MacBook since 2008. She is still awesome even though I am pretty hard on her. But she can be so slow sometimes. Is it possible or even recommended to defrag a Mac? Or something else I can do to fix this?

"Makeuseof" is an ultimate website. It provide new information everyday.
I am using Windows 7. Is there any software or a way to find out who had used my PC in the last couple of day and actually what files had been accessed .

Justin Pot is a technology journalist based in Portland, Oregon. He loves technology, people and nature – and tries to enjoy all three whenever possible. You can chat with Justin on Twitter, right now.